a question about oscillator circuit

[mmajid]

I need a cristal oscillator circuit (Something based on 74HC00 or

74HC04 or similar ones) that can produce a 30MHZ symetric clock

oscillation. Can everybody help me to design one?

What is the principle for choosing suitable resistors and capacitors

in such clock oscillator circuits? I mean can we put

a 30MHZ cristal in a circuit allredy designed for a 10MHZ cristal?

Can I replace such a circuit with a single 30MHZ oscillator?

 

[RadioRon]

I think that 30MHz may be a bit challenging for a simple 74HC type logic gate since the gain of the inverter is dropping off fairly quickly and it might not oscillate. Others with direct experience trying to do this frequency might have more to say. It is worth mentioning that if you must build an oscillator using logic inverters, you really should use the unbuffered type since they have a shorter propagation delay and will oscillate more readily when configured for linear operation. I'm talking about, for example, using the 74HCU04 instead of a 74HC04.

I looked through my oscillator books and could find no logic gate oscillators recommended for frequencies above about 10 MHz except for one rather sophisticated tuned version using 74S series schottky logic. You might want to consider two alternatives. One is to build you own discrete transistor oscillator, and the other is to buy an oscillator ready-built. If you are interested in building a discrete transistor oscillator, please reply and we can recommend some circuits.

 

[docel]

Radioron's right.

Easier to use a DIP Oscillator module (55% duty cycle)